We seek to define and classify hereditary tumors of the nervous system such as occur in neurofibromatosis; to add to the clinical description and natural history of these diseases; to suggest methods for early diagnosis; to evaluate present modes of treatment; and to develop methods for preclinical detection and screening. Our studies have led to the recognition of at least two distinct genetic forms of neurofibromatosis: 1) the classical form as described by von Recklinghausen, and 2) a form in which bilateral acoustic neuromas are the hallmark. Efforts in the latter have been directed at improving and simplifying screening of high-risk individuals, confirming diagnosis, and establishing criteria for intervention. Audiologic studies, including evaluation of auditory-evoked response and acoustic reflex decay, are useful means for early documentation and monitoring of acoustic neuromas. We have recently found that presenile lens opacities or cataracts occur in about 50% of such patients. In our first study involving neurofibromatosis of the von Recklinghausen type, a multi-disciplinary project is nearing completion to evaluate neurologic and cognitive status in these patients compared to their unaffected sibs. We plan to initiate gene-linkage studies in neurofibromatosis, so successful in Huntington disease.